1. Field of the Invention
The present invention relates to a multiple fiber which is excellent in radiation resistance at the region of visible light, and therefore is suitable as an image transmitter of image scope.
2. Description of Prior Art
It has been used in much amount an image scope in the sites where it is possible to receive irradiation, such as an atomic pile, an atomic ship, an artificial satellite and the like.
It is well-known that as the image transmitter of image scope there are two kinds, that is, multiple fibers of silica glass type and multi-component glass type. Between them, the multiple fiber of silica glass type has in general excellent radiation resistance as compared with the multiple fiber of multi-component glass type, and therefore is selectively used for observation in the above mentioned irradiated sites.
According to the studies of the present inventor, however, the radiation resistance of the multiple fibers of silica glass type are various, and are varied by the material which composes of the core.